The kidnapped Egyptian workers, all Coptic Christians, were seized in separate incidents in December and January from the coastal town of Sirte in eastern Libya, which is under the control of Islamist groups.

Islamic State described the Copts it killed as "crusaders".

Libya has been wracked by unrest since the 2011 overthrow of Gaddafi. Since then numerous militia groups have battled for control and the country has two rival governments and parliaments.

The internationally recognised parliament is based in the eastern port of Tobruk, from which Mr Salah reportedly spoke to Al-Arabiya on Friday.

A rival parliament and government are based nearly 1,000km (620 miles) to the west in the capital, Tripoli.

To the east, the city of Benghazi - where the 2011 revolution began - is now largely in the hands of Islamist militants.